Due to the speed of urbanization, more and more fly-overs or overpasses are built above the original traffic roads. There are various special characteristics or requirements to be met by lighting used in such places, such as ease of installation and maintenance, conformity with the construction's overall aesthetic design, anti-vibration considerations. At the same time, the general road lighting requirements should be met, such as no glare, luminance uniformity, average luminance level, etc.
Several lighting solutions are available for the application of fly-overs and overpasses, including high mast lighting and side-wall embedded luminaires.
High mast lighting has been widely and commonly used hitherto for lighting overpasses, but it has several disadvantages, including strong glare caused by the extremely high luminous flux output, difficult and expensive installation and maintenance, inevitable blind-area on the ground due to shading by the fly-over road, low utilization ratio for the fly-over application. Additionally, there is the complaint from drivers and the road lighting administrator that flourishing roadside trees block the light from the road lighting luminaire on the pole and have a negative impact on the overall luminance level and luminance uniformity, which reduces driving safety accordingly.
A side-wall embedded luminaire is another commonly used lighting option. It generally uses fluorescent lamps as the light source, and is embedded in the side wall fence at a low mounting height. It has several disadvantages, including an insufficient illuminance level for driving safety and poor illuminance uniformity.
Recently, Thorn Lighting Co. Ltd. issued a low-height mounted luminaire bearing the brand name of Orus, which is claimed to provide an anti-glare lighting solution to ramps or bridges. The luminaire uses a ceramic metal halide lamp as the light source, and its optical structure is mainly made up of a cylinder-shaped reflector, which is claimed to achieve uniform illuminance on road surfaces. However, the inventors of the present invention have observed the following disadvantages of such a luminaire:
As a light source, the ceramic metal halide lamp is large in size and shape, making it difficult for the optical design to control light intensity and/or light distribution. Moreover, the emitting surface is very bright. Therefore, direct, strong light radiation from the luminaire to the driver of an automotive vehicle is unavoidable, which causes visual discomfort to the driver's eyes, such as flickering, and hence causes safety problems.
In practical deployments, the luminaire cannot provide a satisfying level of luminance uniformity on road surfaces.
Additionally, the whole luminaire is relatively large in size and protrudes from the side-wall fence, which results in a negative effect on pedestrians and/or passing vehicles.